Interventional Procedure

Say you are considering the introduction of a new procedure such as endovascular stenting for treatment of abdominal aortic aneurysm. The new technique poses both opportunities and resource implications for your department. You want to know whether the new technique is effective and safe before you will consider introducing it. In plain English the question might be worded "Is stenting as good as or better than surgery for aneurysms?" While that is a valid question, it does not lend itself to a literature search. A search of Pubmed using the string "stent* AND surgery AND aneurysm*" yields 1156 citations (the wildcard symbol * allows you to include multiple similar words in a search strategy with one term - "stent*" would include "stent", "stents" and "stenting"). It would be impossible to look through all of these and in any case the vast majority of them would have nothing to do with the current question.

Applying the PICO approach we might construct a question as follows:
"In patients with abdominal aortic aneurysms [Patient] is endovascular aneurysm repair [Intervention] as good as open surgical repair [Comparison] in terms of morbidity, mortality, length of ICU stay, length of hospital stay, graft failure and cost / impact [Outcome]?" This is illustrated in the table below.

This is a much more focused question. In fact there are six focused questions, related to the six outcomes of interest. It also makes it easier to develop a search strategy that will yield a smaller number of more relevant papers. Searching is described in greater detail in another part of this site, but for the moment it is sufficient to know that "Boolean operators" such as "AND" and "OR" can be used to refine a search strategy. These are fairly intuitive concepts; when "AND" is placed between two terms in a search strategy, the search will only return citations that contain BOTH terms. If "OR" is used then the search will return citations that contain EITHER of the terms. The general principle in formulating the search is to place "AND" between terms in each column of the PICO table and to place "OR" between terms within each column, as illustrated below:

Patient		Intervention		Comparison		Outcome
Abdominal aortic aneurysm	AND	Endovascular aneurysm repair	AND	Open surgical repair	AND	Morbidity OR Mortality OR ICU stay OR Hospital stay OR Graft failure OR Cost / Impact

This example is further developed in the section on searching, where we describe how to turn this into a Pubmed search.